This invention generally relates to an apparatus for crimping pipes. The preferred embodiment of the invention particularly relates to an apparatus for crimping the leading edge of continuously produced, spirally formed pipe.
Lightweight metal pipes are widely used for ventilation ducts. U.S. Pat. Nos. 4,567,742 (Castricum) and 3,132,616 (Hale) disclose two types of machine for continuously producing spirally formed metal pipes. Each machine uses a continuous, flat strip of metal as a starting material. A drive means feeds the metal strip into and through the pipe forming machine. The strip first passes through a series of metal forming rollers which bend the outer edges of the strip into predetermined shapes. Next, the metal strip passes around a forming head or mandrel in a spiral manner, so that strip forms a spiral-shaped cylinder with the outer edges of the strip adjacent each other. The adjacent edges of the strip are then compressed to form a metal pipe having a spiral or helical lockseam.
The spiral (helical) pipe is formed continuously in this manner as long as the metal strip is fed through the machine. It should be understood that during the pipe forming process the pipe and its leading edge move spirally, that is, they rotate and move forward in the axial direction of the pipe at the same time. The trailing edge of the pipe being formed remains in the forming head of the machine.
It should also be apparent that this type of spiral pipe forming machine can make pipe of any desired length. When the continuously formed pipe reaches its desired length, it is severed. A preferred apparatus for cutting spiral pipe is disclosed in my co-pending U.S. patent application, Ser. No. 876,286, filed June 15, 1986, which is a continuation-in-part of application Ser. No. 746,237, filed June 18, 1985, now abandoned. This preferred pipe cutting apparatus cuts a section of pipe with minimal interruption to the pipe forming process.
Frequently, a plurality of pipe sections must be joined together to extend across a long expanse. One method of joining pipe sections is to crimp the circumferential edge at one end of a pipe section. The crimped edge will have a series of corrugations around its circumference, which will be slightly smaller in diameter than the uncrimped part of the pipe section. The crimped end of one pipe section should fit snugly into an uncrimped opening of another pipe section. In this manner a plurality of similarly shaped pipe sections, each having a crimped end and an uncrimped end, can be easily connected together in series.
The assignee of the present invention presently uses a pipe crimping machine that is separate from, and operates independently of, the pipe forming machine. This crimping machine has an upper crimping roller and a lower crimping roller mounted adjacent each other. Each roller has a plurality of teeth spaced around its circumference, so that each roller looks like a gear. The lower roller can be moved towards or away from the upper roller. When the rollers are apart, one end of a pipe section is inserted between the rollers. The lower roller is then moved towards the upper roller until the teeth of the two rollers crimp and grip the pipe. One of the rollers is then mechanically driven, so that it rotates the pipe between the two rollers and the entire circumference of the pipe is crimped. The rollers are then separated and the pipe section removed from the crimping machine.
While this type of crimping machine serves its intended purpose of crimping the end of a pipe section, it has some disadvantages. Primarily, this type of crimping machine requires manual operation. Someone must physically take each section of cut pipe from a discharge rack adjacent the cutting machine, carry it to the crimping machine, crimp one end of the pipe, and then store the crimped pipe at another location. These manual steps become increasingly difficult as the length of the pipe section increases.
Thus, when pipe sections become rather long, for example, 20 feet, alternatives to crimping may be used to connect pipe sections. One such alternative is a separate connector piece. The connector may be a short section of pipe (approximately four inches long) having a diameter that is slightly smaller than the diameter of the uncrimped ends of the pipes sections to be joined. A raised circumferential bead is provided near the middle of the connector. The outer diameter of the bead is slightly greater than the diameter of the pipe sections. Thus, adjacent pipe sections are slid over opposite ends of the connector until they abut the central bead. Screws or other fastening means are used to secure both pipe sections to the underlying connector.
This type of connector also has its disadvantages. For example, it requires the manufacture of an additional part--the connector. Additional labor is required for drilling holes in the pipe sections and connector for the screws, and for fastening the screws. Having an exposed connector in both pipe sections will also provide an interruption or obstacle to the flow of fluid through the pipe, regardless of the direction of the fluid flow.